Post here the achievements that you would find cool in the game. Personally i think they should go easy on the solid online achievements, still have some in there but not really insanely hard ones. Here are my ideas.

Beat Arcade Mode with X - 5G (Do this for every character)

Roster run through - Complete arcade mode with all charcters

The King of Iron Fist Fighter - Complete Arcade on Hardest difficulty (allowed to continue)